The Bangkok Post cited a statement issued by the Royal Household Bureau before midnight as saying that a tube inserted in the monarch’s abdomen earlier this month was re-adjusted for the 75-minute long procedure Friday night.

The tube had reportedly been placed in the abdomen of the world’s longest reigning monarch to drain excess cerebrospinal fluid around his spine.

Friday’s procedure was conducted after the king exhibited facial twitching and an x-ray revealed fluids around his brain.

Adulyadej, who is venerated as a demi-God by the majority of Thais, has repeatedly been placed under medical care since being hospitalized for flu and pneumonia in 2009.

The king has spent some time outside of the medical ward by traveling to his seaside ‘Far From Worries’ palace in Hua Hin, 200 kilometers (124 miles) south of Bangkok.

He was diagnosed with an intestinal inflammation in 2011 before suffering subdural bleeding in the front of his brain the following year.

Each health alert is cause for anxiety among Thai people, the majority of whom were born under his reign, which started in 1946 following the mysterious death of his brother, King Ananda, who was found dead with a bullet wound to his head in his bedroom.

In January, the king made a trip of several hours to his Bangkok palace, his first outing in months.

In December, he presided over a televised swearing-in ceremony for judges held at the hospital where he is receiving treatment.

Adulyadej represents a unifying figure among the country's tenuous, military-controlled politics, and many Thais worry about the likely succession.

Crown Prince Vajiralongkorn -- 63, who divorced his third wife in 2014 -- is much less popular than his father.

The tense political climate following the May 22, 2014 coup that overthrew an elected government, and deep divisions in the country between supporters of the traditional elite and those who want social change, have added to the sensitivity of the royal succession.